Chapter 12: Upgrading and Recompiling Kernels

Overview

The thought of recompiling a kernel strikes fear into many Linux users. It is true; errors can lead to an unbootable system. If you don’t have an appropriate backup, recovery can be difficult. But with a few simple precautions, you can avoid risks when you recompile a kernel. Once you understand the basic steps, it is not a difficult process.

There is an easy way to upgrade a kernel: just install the next version of the Red Hat kernel RPM that’s customized for your CPU. The Red Hat RPM automatically updates your bootloader so you can start Linux with either the old or the new kernel.

The Red Hat kernel RPM may not include the very latest upgrades. The latest Linux kernels are available in tarball format; alternatively, minor upgrades only require a patch. Both options are described in this chapter.

You can customize and recompile the kernel already on your computer, or you can download, customize, and recompile a new kernel. The wide variety of options makes this process seem more difficult than it really is. In this chapter, you’ll learn about three different “make” kernel configuration tools.

This chapter includes a detailed analysis of what you can change, based on the GUI kernel configuration tool. This tool is organized into configuration menus, storage devices, networking, other hardware support, and other software support categories.

I’ve included a number of different kernel version numbers. The Linux kernel version released with Red Hat 9 is 2.4.20. Some version numbers in this chapter may be higher, which can reflect the changes that you or a colleague may already have made.

Once you’ve made the desired changes, you need to compile your new kernel. It’s a straightforward, step-by-step process. After compiling the kernel, you’ll want to copy it to the appropriate directories. At least for now, you’ll also want to configure it into your bootloader as though the old and new kernels were two different operating systems. This chapter covers the following topics:

Why bother?

Choosing the easy way

Exploring tarball and patch alternatives

Setting up configuration menus

Understanding kernels, section by section

Compiling your new configuration

Updating the bootloader